One great 'Naruto Momoshiki Otsutsuki fanfiction' is 'The Otsutsuki's Ascent'. It delves deep into Momoshiki's backstory and his interactions with the Naruto universe in a really interesting way.
Power is a common theme. Since Momoshiki is such a powerful character, many fanfictions explore how his power affects the Naruto world and the characters in it.
There's a really interesting one where the author gives a different perspective on the fight. It's called 'Naruto and Sasuke vs Momoshiki: An Alternate View'. It focuses more on the strategic aspects of their combat that the anime might not have fully explored.
It's appealing because we get to see more of the characters' thoughts and feelings during the fight. In the original series, there are limitations on how much of their internal monologues can be shown. Fanfictions fill that gap. For example, a fanfiction might show Naruto's doubts and how he overcomes them during the battle with Momoshiki. Also, some fanfictions might explore different relationships between Naruto, Sasuke and other characters in the context of this battle, like how their teamwork affects the fight in ways not shown in the anime or manga.
It depends on the context. If it's a battle of pure physical strength and chakra, Naruto might have the edge as he has years of experience and has faced more powerful foes. But Boruto has some unique abilities like his Jougan. So if the fight involves using new - age ninja techniques, Boruto could surprise Naruto.
Maybe a fanfic where Naruto and Boruto are pitted against each other in a virtual reality battle. It could be part of a training exercise that gets out of control, and they start using their real skills and emotions, leading to a intense and revealing fight.
I really liked 'A New Beginning for Momoshiki in Naruto'. This fanfiction takes an interesting turn where Momoshiki is reincarnated in a different form and has to navigate the world of Naruto from a different perspective. It's full of action and also some great character development for Momoshiki. Also, 'Momoshiki and Naruto: Unlikely Allies' is a great read as it focuses on how their powers could combine in unexpected ways.
There are fanfictions where Momoshiki and Naruto interact in unique ways. Maybe Momoshiki has some knowledge that Naruto needs, and they have to negotiate. Their power levels are compared and contrasted. Naruto's ability to use Sage Mode and his chakra reserves are pitted against Momoshiki's alien - like powers. It creates a dynamic where both characters are forced to adapt to each other's fighting styles.
There could be physical changes too. Naruto might have a new form that combines his own features with Momoshiki's. His body could become more resilient, like Momoshiki's, and he might have a different chakra signature. This new form could attract the attention of other villains in the Naruto universe, either out of fear or the desire to steal his power. Moreover, his relationships with other characters like Sasuke could be affected, as they have to adapt to this new Naruto who has absorbed Momoshiki.
For the ninja world in the fanfiction, it might bring a sense of peace as Momoshiki was a powerful threat. However, it could also lead to new enemies emerging, seeking revenge for Momoshiki's death. Naruto might also have to deal with the political fallout, as some villages might see his act as an overstep of power or a sign of aggression.